The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft is moved by several turbojet engines each housed in a nacelle accommodating an assembly of auxiliary actuating devices relating to its operation and ensuring various functions when the turbojet engine is in operation or shut-down.
In particular, these auxiliary actuating devices comprise a mechanical thrust reverser system.
In general, a turbojet engine nacelle presents a substantially tubular structure comprising an air inlet upstream of the turbojet engine, a mid-section intended to surround a fan of said turbojet engine, a downstream section intended to surround the combustion chamber of the turbojet engine and possibly integrating thrust reversal means, and is generally terminated by an ejection nozzle whose outlet is located downstream of the turbojet engine.
Modern nacelles are intended to accommodate a bypass turbojet engine capable of generating via the blades of the rotating fan a hot air flow (primary flow) and a cold air flow (secondary flow) which circulates outside the turbojet engine through an annular passage, also called flow path, formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two air flows are ejected from the turbojet engine from the rear of the nacelle.
The role of a thrust reverser, during the landing of an aircraft, is to improve the braking capability of said aircraft by redirecting forwards at least one portion of the air ejected from the turbojet engine. In this phase, the thrust reverser obstructs at least one portion of the flow path of the cold flow and directs this flow forwardly of the nacelle, thereby generating a counter-thrust which is added to the braking of the wheels and air brakes of the aircraft.
In general, the structure of a thrust reverser comprises a thrust reverser cowl displaceable between, on the one hand, a reverse jet position in which it opens in the nacelle a passage intended for the diverted air flow, and on the other hand, a direct jet position in which it closes this passage.
Besides being involved in a thrust reversal function, by belonging to the rear section of the nacelle, a thrust reverser movable cowl includes de facto a downstream portion forming the ejection nozzle.
The section of the ejection nozzle may be adapted according to the different flight phases, namely in particular the take-off, the climb, the cruise, the descent and the landing in order to always preserve an optimum nozzle section depending on the operating speed of the turbojet engine. The nozzle will be then called variable nozzle.
Such a variable nozzle is associated to an actuation system allowing this section variation.
There are several solutions to make a variable nozzle.
A first solution is to provide pivoting terminal flaps mounted on the movable thrust reverser cowl and whose pivoting results in an increase or a reduction of the outlet section. Such a system is described in particular in the documents FR 2 929 998 and FR 2 934 326.
There are also known panels movably mounted in translation inside the movable thrust reverser cowl, in a telescopic manner, whose retreat or retraction similarly results in the increase or the reduction of the outlet section.
In the context of a thrust reverser provided with a variable-section nozzle, it is known to actuate the deployment of the movable cowl and the variation mechanism of the section of the variable nozzle by the same cylinders, the movable cowl and the variable nozzle being selectively coupled and uncoupled by a locking device.
This locking device selectively links the thrust reverser cowl and the variable nozzle in a rigid manner, the variable nozzle being free when the thrust reverser cowl is locked on the fixed structure of the thrust reverser in its direct jet position, and the variable nozzle being coupled on the cowl when the cowl is unlocked, so that the nozzle and the cowl are simultaneously driven in displacement.
In general, this type of locking device is relatively complex, it often requires an alignment of different parts to allow the coupling of the cowl and of the variable nozzle.
The large number of parts of this type of coupling device can be a source of failure and often leads to an average reliability.